Worldwide water shortage is becoming severe. Thus, large attention has been paid to desalination process. Conventional desalination process has a problem of the discharge of high salty waste seawater. The discharge from desalination process might damage the environment due to the salinity. Hence, to reduce the amount of the discharge, the increase in recovery ratio, defined as the ratio of product to feed water flow rate, is required. However, increasing the recovery ratio, scale deposits on heat transfer surface. Scale is precipitation of salts in seawater, which deteriorates the heat transfer inside heat exchanger. Therefore, the recovery ratio in conventional processes is generally restricted to 50%. Simultaneously, the energy consumption of conventional desalination process is high. Thus, the further energy saving is required.

 In order to prevent the scale deposition and reduce the discharge of high salty waste seawater in desalination process with high energy efficiency, a self-heat recuperative desalination process using fluidized bed was proposed. In the process, the fluidized bed is employed as an evaporator, in which the heated particles are fluidized by blown gas and contact seawater fed from the top of the bed. Then, the seawater evaporates on the heated fluidized particles instead of heater surface. Thus, it can be considered that the seawater desalination process using fluidized bed evaporator can prevent the scale deposition on the heater surface. However, the process might cause defluidization when an excessive amount of liquid feeds into the fluidized bed evaporator. When the defluidization takes place, the seawater evaporation does not continue.

 So far, in order to examine the scale prevention capability and the defluidization phenomena, the seawater evaporation experiment in lab-scale fluidized bed was conducted. The results showed that the proposed process has large scale prevention capability and the large fluidizing gas velocity can avoid the defluidization. However, the large fluidizing gas velocity increases blower work in the process. To operate a stable and energy efficient desalination process, the mechanism of heat transfer and evaporation for fluidization in the bed is investigated. The fed seawater agglomerates small amount of fluidized particles, stirred by fluidizing gas and receives the heat for evaporation from the bed. During the evaporation process, operation conditions such as bed temperature, fluidizing gas velocity and so on, have large influence on fluidization and energy consumption. Therefore, from this analysis of the fluidized bed, the optimum conditions for the proposed desalination process are examined.